Frequently Asked Questions






    General
  1. How does a geothermal system work?
    Throughout the year, outdoor temperatures fluctuate with the changing seasons. However, underground temperatures do not. In fact, about four to six feet below the earth's surface, temperatures remain relatively constant year-round. A geothermal system, which consists of an indoor unit and a buried earth loop, capitalizes on these constant temperatures.
    In the winter, fluid circulating through the system's earth loop absorbs stored heat and carries it indoors. The indoor unit compresses the heat to a higher temperature and distributes it throughout the building. In the summer, the system reverses, pulling heat from the building, carrying through the earth loop and depositing it in the cooler earth.
  2. What makes a geothermal system different from conventional systems?>
    A geothermal system utilizes the energy from the sun, which is stored in the earth, to heat and cool homes and buildings. Typically, electric power is used only to operate the unit's fan, compressor and pump. So, unlike conventional systems, geothermal systems do not burn fossil fuel to generate heat--they simply transfer heat to and from the earth.
  3. How efficient is a geothermal system?
    A geothermal system is more than three times as efficient as the most efficient conventional system. Because geothermal systems do not burn combustible fuel to make heat, they provide three to four units of energy for every one unit used to power the system.
  4. What does geothermal mean to the environment?
    Because geothermal systems work with nature, not against it, they minimize the threats of acid rain, air pollution and the greenhouse effect. An environmentally friendly fluid is used in the closed, continuous loop.
  5. Do geothermal systems require much maintenance?
    No. In fact, geothermal systems are practically maintenance free. When installed properly, the buried loop will last for generations. And the other half of the operation--the unit's fan, compressor and pump--is housed indoors, protected from the harsh weather conditions. Usually, periodic checks and filter changes are the only required maintenance.
    Heat Pumps: What are they and how do they work?
  1. What is a geothermal heat pump?
    A geothermal heat pump is an electrically-powered device that uses the natural heat storage ability of the earth and/or the earth's groundwater to heat and cool your home or business.
  2. How does it work?
    Like any type of heat pump, it simply moves heat energy from one place to another. Your refrigerator works using the same scientific principle. By using the refrigeration process, geothermal heat pumps remove heat energy stored in the earth and/or the earth's groundwater and transfer it indoors.
  3. How is heat transferred between the earth and the home or building?
    The earth has the ability to absorb and store heat energy. To use that stored energy, heat is extracted from the earth through a liquid medium (groundwater or an anti-freeze solution) and is pumped to the heat pump or heat exchanger. There, the heat is used to heat the air. In summer, the process is reversed and indoor heat is extracted from indoors and transferred to the earth through the liquid.
  4. Does it do both heating and cooling?
    One of the things that makes a heat pump so versatile is its ability to be a heating and cooling system in one. You can change from one mode to another with a simple flick of a switch on your indoor thermostat. In the cooling mode, a geothermal heat pump takes heat from indoors and transfers it to the cooler earth through either groundwater or an underground loop system.
  5. Do I need separate ground loops for heating and cooling?
    No. The same loop works for both. All that happens when changing from heating to cooling, or vice versa, is that the flow of heat is reversed.
  6. What types of loops are available?
    There are two main types: open and closed. The next two sections will give you specifics about each.
  7. Does the underground pipe system really work?
    The buried pipe, or "ground loop," is the most recent technical advancement in heat pump technology. The idea to bury pipe in the ground to gather heat energy began in the 1940s. It's only been in the last few years that new heat pump designs and improved pipe materials have been combined to make geothermal heat pumps the most efficient heating and cooling systems available.
    Closed-loop systems
  1. What is a closed-loop system?
    The term "closed-loop" is used to describe a geothermal heat pump system that uses a continuous loop of special buried plastic pipe as a heat exchanger. The pipe is connected to the indoor heat pump to form a sealed, underground loop through which an antifreeze solution is circulated. Unlike an open-loop system that consumes water from a well, a closed-loop system recirculates its heat-transferring solution in pressurized pipe.
  2. Where can this loop be located?
    That depends on land availability and terrain. Most closed–loops are trenched horizontally in yards adjacent to the building. But any area near a home or business with appropriate soil conditions and adequate square footage will work.
  3. How deep and long will my trenches be?
    Trenches are normally four to six feet deep and up to 400 feet long, depending on how many pipes are in a trench. One of the advantages of a horizontal loop system is being able to lay the trenches according to the shape of the land. As a rule of thumb, 500-600 feet of pipe is required per ton of system capacity. A well-insulated 2,000 square–foot home would need about a three-ton system with 1,500 — 1,800 feet of pipe.
  4. How many pipes are in a trench?
    Normally, a run of pipe is laid at five feet then looped back over itself at three feet once the bottom pipe is covered with soil. This allows more length of pipe to be put in one trench and has no adverse affect on system efficiency. Other loop designs use four or six pipes and allow for shorter trenches if land area is limited.
  5. What if I don't have enough room for a horizontal loop?
    Closed-loop systems can also be vertical. Holes are bored to about 125-150 feet per ton of heat pump capacity. U-shaped loops of pipe are inserted in the holes. The holes are then backfilled with a sealing solution.
  6. How long will the loop pipe last?
    Closed-loop systems should only be installed using high density polyethylene or polybutylene pipe. Properly installed, these pipes will last for many decades. They are inert to chemicals normally found in soil and have good heat conducting properties. PVC pipe should not be used under any circumstances.
  7. How are the pipe sections of the loop joined?
    The only acceptable method to connect pipe sections is by thermal fusion. Pipe connections are heated and fused together to form a joint stronger than the original pipe. Mechanical joining of pipe for an earth loop is never an accepted practice. The use of barbed fittings, clamps, and glue joints is certain to result in loop failure due to leaks.
  8. Will an earth loop affect my lawn or landscape?
    No. Research has proven that loops have no adverse effect on grass, trees, or shrubs. Most horizontal loop installations use trenches about six inches wide. This, of course, will leave temporary bare areas that can be restored with grass seed or sod. Vertical loops require little space and result in minimal lawn damage.
  9. Can I reclaim heat from my septic system disposal field?
    No. An earth loop will reach temperatures below freezing during extreme conditions and may freeze your septic system. Such usage is banned in many areas.
  10. Can I install an earth loop myself?
    It's not recommended. In addition to thermal fusion of the pipe, good earth-to-coil contact is very important for successful loop operation. Nonprofessional installations may result in less than optimum system performance.
  11. I have a pond nearby. Can I put a loop in it?
    Yes, if it's deep enough and large enough. A minimum of six feet in depth at its lowest level during the year is needed for a pond to be considered. The amount of surface area required depends on the heating and cooling load of the structure.
    Open–loop systems
  1. What is an open-loop system?
    The term "open-loop" is commonly used to describe a geothermal heat pump system that uses groundwater from a conventional well as a heat source. The groundwater is pumped into the heat pump unit where heat is extracted, then the water is disposed of in an appropriate manner. Since groundwater is a relatively constant temperature year-round, it is an excellent heat source.
  2. What do I do with the discharge water?
    There are a number of ways to dispose of water after it has passed through the heat pump. The open discharge method is the easiest and least expensive. Open discharge simply involves releasing the water into a stream, river, lake, pond, ditch, or drainage tile. Obviously, one of these alternatives must be readily available and must possess the capacity to accept the amount of water used by the heat pump before open discharge is feasible.
    A second means of water discharge is the return well. A return well is a second well bore that returns the water to the ground aquifer. A return well must have enough capacity to dispose of the water passed through the heat pump. A new return well should be installed by a qualified well driller. Likewise, a professional should test the capacity of an existing well before it is used as a return.
  3. How much groundwater does an open-loop system need?
    Geothermal heat pumps used in open-loop systems need differing amounts of water depending on the size of the unit and the manufacturer's specifications. The water requirement of a specific model is usually expressed in gallons per minute (g.p.m.) and is listed in the specifications for that unit. Your heating contractor should be able to provide this information. Generally, the average system will use 1.5 g.p.m. per ton of capacity while operating.
    Your well and pump combination should be large enough to supply the water needed by the heat pump in addition to your domestic water requirements. You will probably need to enlarge your pressure tank or modify your plumbing to supply adequate water to the heat pump.
  4. What problems can be caused by poor water quality?
    Poor water quality can cause serious problems in open-loop systems. Your water should be tested for hardness, acidity and iron content before a heat pump is installed. Your contractor or equipment manufacturer can tell you what level of water is acceptable.
    Mineral deposits can build up inside the heat pump's heat exchanger. Sometimes a periodic cleaning with a mild acid solution is all that's needed to remove the build-up.
    Impurities, particularly iron, can eventually clog a return well. If your water has a high iron content you, should be sure that the discharge water is not aerated before it's injected into a return well.
    Finally, you should opt against using water from a spring, pond, lake or river as a source for your heat pump system unless it's proven to be free of excessive particles and organic matter. They can clog a heat pump system and make it inoperable in a short time.
  5. Does an open-loop system cause environmental damage?
    No. They are pollution free. The heat pump merely removes or adds heat to the water. No pollutants are added whatsoever. The only change in the water returned to the environment is a slight increase or decrease in temperature.
    Some people are concerned that open-loop systems contribute to the depletion of our ground water resources. This issue is not critical in some parts of North America because of abundant supplies of ground water.
  6. Are there any laws that apply to open-loop installations?
    In some localities, all or parts of the installation may be subject to local ordinances, codes, covenants or licensing requirements. Check with local authorities to determine if any restrictions apply in your area.

































































































































































































































































































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Copyright 2011 by Geothermal Specialist, Inc.
Last Updated: February, 2011